When loosening a threaded bolt or nut, several times the amount of torque used to tighten it may be required to free the fastener. There are several reasons why this happens. One reason it that a standard V-thread is a self-locking thread. When a threaded fastener ages, it can corrode, and the threads will bind when trying to remove it. This is a problem for any equipment which is outdoors or in a corrosive environment. Another reason is that bonding agents, such as Loctite® adhesives from Henkel Corp. of Gulph Mills, Pa., are widely used to keep fasteners from vibrating loose. Bonding fluids work well, but make it even more difficult to remove the fastener. Impact guns are often used to remove these fasteners, and they work well if there is enough space to fit the gun with the socket disposed in the correct position over the fastener. Impact guns are becoming progressively more difficult to use because most machinery is getting smaller and more compact.
Prior art in this field uses mechanisms which allow only a line contact between the ram and lever. U.S. Pat. No. 3,273,428 to Rudeke shows contact between an anvil block 22 and a lug 23. The anvil block 22 has a flat surface, and the lug 23 has a rounded surface. This arrangement results in line contact through the stroke of the anvil block. U.S. Pat. No. 6,502,485 to Salazar shows contact between a striking pin 37 and a ratchet wrench head 34. The striking pin 37 has a flat contact surface and the ratchet wrench head 34 also has a flat surface which is rotatable. This arrangement results in line contact through almost the entire stroke. There is only one position in the stroke arrangement, i.e., when the two flat surfaces are parallel, where there is a rectangular area of contact between the striking pin 37 and the ratchet wrench head.
In this type of application, forces are very high. In order to reduce stress, contact area must be maximized. Line contact between two parts results in very low contact area which results in a poor transfer of impact and premature failure.